Change detection is used to identify areas of differences among images of the same region that were collected at different times. Changes that can be identified include new construction, movement of man-made objects, and roadway additions or alterations. The basic steps in prior art change detection techniques are: image pre-processing, image registration, change determination, and change display. A common approach for the change determination step is to simply subtract the first image from the second image. The difference in areas of change will be large. The difference in areas of little or no change will be small (or zero). See, Remote Sensing and Image Interpretation, by Lillesand, T. M., Kiefer R. W., page 621, John Wiley and Sons, 1994. The shortcoming of this process is that the images have to be precisely registered before the subtraction step or there will be indications of change where no actual change occurred. These false change indications sometimes appear as outlines around objects.
There is a need therefore for an improved technique for the change determination step in the change detection process.